Rice under center pivots

Pockmarked with earthquake-caused sand blows and unable to hold a flood, traditional rice production is not an easy proposition in some fields around Portageville, Mo.

But studies at the University of Missouri Delta Research Center are increasing hope for an untraditional production method: rice under center pivot.

This area in southeast Missouri’s Bootheel “is earthquake country,” says Gene Stevens, Extension agronomist at the center. “We’re in Pemiscot County and are on the fault line. In some fields, the soil is all clay with one sandy spot. The pivot could provide farmers an opportunity to grow rice in areas where they couldn’t before.”

It’s true the pivot may save water and energy. “But the main benefit might be to expand producers’ crop mix and rotation possibilities. The more options for the farmer, the better.”

The field being used for the study couldn’t feasibly grow flooded rice. “It won’t maintain a flood. You’d have to constantly pump and it would be cost-prohibitive,” says Earl Vories, USDA-ARS agricultural engineer at the center.

Several years ago, a confluence of research, state and business interests came together for the center pivot studies. Stevens was approached by the Missouri Department of Natural Resources (DNR) looking for technologies that might save resources as part of the state’s soil and water tax.

At the same time, Vories — unaware of Stevens’ DNR contacts — was talking with Valley Irrigation engineer, Jake LaRue. “Valley has an interest in rice under a pivot, obviously, since they sell pivot equipment. Between Valley and DNR, and with help from the local Valley dealer, Mid Valley, we pulled it all together for the research.

Valley actually donated a pivot in order to do the studies while DNR provided operating funds for three years.”

The pivot was put up in May 2008 specifically for the study. There are about 18 acres under the system.

One main objective of the project is to study nitrogen efficiency. At the same time, researchers are also studying water use — Vories’ main emphasis.

“We’ve been comparing split applications of dry urea to fertigation,” says Stevens. “We’re seeing rice yields are much better with the fertigation — probably because we can split it more.”

In 2008, “we had a RiceTec hybrid and two conventional, self-pollinating varieties. We are using Clearfield technology, so were hoping Beyond and Newpath would be helpful for weed control.”

The biggest weed problem has proven to be pigweeds — especially Palmer amaranth — which, due to glyphosate resistance, is also a big problem in Bootheel cotton and soybean fields.

Unfortunately, “Palmer amaranth is also resistant to ALS herbicides, which Beyond and Newpath fall under. When we began spraying last year, they provided little help in control. So, we had to go back to more conventional rice herbicides.

“The biggest issue we’ve found with Palmer amaranth is spraying early. You’ve got to get them when they’re still small. If they get even a little bit ahead, you’ve lost the battle.

“Last year, we learned a lot about weed control in this system and carried it into this year. This time around, we’ve done a really good job keeping the field clean.”

In 2008, the researchers didn’t have a “really systematic” way of irrigating, says Stevens. “It was more walking out there and seeing if anything was sticking to your boots.”

This year, Vories has been working closely with the University of Arkansas to develop water-use coefficients for the Arkansas irrigation scheduler. Stevens believes that’s one reason the rice “looks so good currently — we’re doing a better job of watering it.”

Last year, as a check, another rice field was planted the same time, using the same varieties and nitrogen treatments (except for fertigation) as the field under pivot. It turned out the pivot saved about 30 percent of the water compared to the flood.

“Quite honestly, I’m not sure we’ll save as much water this year,” says Vories.

Why is that?

“The main thing is not starving the crop for water. We don’t want to hurt the production. We’ve been using the irrigation scheduler but a lot of guess work has to be done at the outset of this research. So we’ve placed soil moisture sensors in the test field.

“We want to gain some confidence in our tweaks of the scheduler before trying to withhold water. There’s a good chance we’ve over-applied water this season. The soil we’re working has some very sandy spots and those have to be watched closely.”

The pivot will still provide water savings and there’s probably room to cut back “but we won’t do that at the expense of the rice yield. We’ll evaluate that at the end of the season. That’s one thing that (LaRue) at Valley will help with. We’ll gather the soil moisture records, the irrigation scheduler records and compare all that data. Going into next year, we’ll have a better idea of how to proceed.”

As in much of the Mid-South, plentiful early rains this spring kept the researchers from planting as early as they’d have liked. Then it turned off dry and “we had to irrigate every other day for a while,” says Stevens. “Lately, it’s been wet again so we haven’t been watering as much. The season has really been a mixed bag with moisture.

“The crop looks really good, though. The whole circle is in rice this year — last year it was only half in rice.”

Also in the study are large strips of conventional rice varieties that farmers would recognize.

“We’ll harvest those using a yield monitor and later be able to compare how the soil types vary under the pivot and varietal response,” says Vories. “That should help point out — depending on what soil you want to try the pivot on — what rice variety should be planted.”

To grow rice, have there been any modifications to the pivot? Any the researchers would like to see?

“In other locations where rice is being grown under pivot, modifications mainly have to do with the wheels at the towers,” says Vories. “We have one tower that has four wheels instead of the traditional two. Another site uses three tires. Another site is looking at a system with tracks.

“Rice is going to have soil that’s a bit wetter than you’d see with soybeans or cotton. So, to keep from making big ruts the flotation modifications are needed.”

Stevens says that when talking with specialists from other states, one of the major concerns about growing rice under pivot is blast. “Some research was done in the late 1980s in Louisiana and Texas using this system. The rice was nailed with blast. Wet foliage is conducive for that.”

One of the tools to deal with blast is increased water depth.

However, “since we’re not flooding the rice that isn’t an option. One of the reasons we used a RiceTec variety is it is supposed to be more resistant to blast. We’re also checking out Templeton, a new release from (the University of) Arkansas that is supposed to have more blast resistance.”

A chemigation with Quadris has already been applied. However, that wasn’t done for blast, but rather for brown spot in the Wells plots.

“If I was a grower contemplating this system, I’d definitely find the best disease packages and be prepared to put out late-season fungicides for disease control,” says Stevens.

One nice thing about the pivot system is the fungicides labeled to be put out in water. “It makes it simple to make an application since you’ll be irrigating anyway,” says Vories.

With weed chopping/pulling crews an increasingly common sight in Bootheel fields, Stevens returns to the importance of controlling weeds early in the production system. “I can’t emphasize that enough.”

He also suggests a strict irrigation campaign. “A lot of farmers’ approach to irrigation is, ‘Well, it’s hot today and hasn’t rained this week — it must be time to irrigate.’ I really encourage a more systematic approach, maybe to use some sort of irrigation scheduling program.”

In 2008, “we had some rice under the pivot’s end-gun. The end-gun didn’t come on for a week” and harmed that portion of the crop.

“If you grow rice under pivot, you don’t have time to wait for a part to come in two weeks later. Repairs need to be done quickly. So far, I believe this system requires greater management than conventional rice.”